1. Field of the Invention
The present invention generally relates to a fluid handling apparatus and a fluid handling unit for use therein. More specifically, the invention relates to a fluid handling apparatus capable of being used as a sample analyzing apparatus for analyzing samples, such as biosubstances representative of functional substances, and a fluid handling unit for use therein.
2. Description of the Prior Art
As conventional methods for specifically detecting biosubstances, such as proteins, there are known various methods for causing an antigen-antibody reaction using an antibody to a specific biosubstance, to carry out the visual recognition or spectroscopic measurement of a reactant thus obtained, to detect the biosubstance.
As methods for quantifying a reactant obtained by an antigen-antibody reaction of a biosubstance, such as a protein, there are widely adopted some methods, such as ELISA (Enzyme-Linked ImmunoSorbent Assay). In these methods, there is used a sample analyzing apparatus called a microplate wherein a large number of fine recessed portions generally called microwells (which will be hereinafter referred to as “wells”) are arrayed. The wall surfaces of the wells are coated with an antibody to a specific biosubstance, which is a target substance, as a capturing (or catching) material, to capture (or catch) the target substance by the capturing material to detect the target substance by measuring a reactant, which is obtained by an antigen-antibody reaction between the target substance and the antibody, by fluorescence, luminous reagents or the like.
In a typical method using a microplate, such as ELISA, the absorbance or fluorescence of a liquid obtained by an antigen-antibody reaction is measured. In this case, a value obtained by optical measurement depends on the quantity of the liquid if the liquid is a dilute solution. That is, the value obtained by optical measurement is in proportional to the height of the liquid, which is filled in a well, from the bottom of the well to the liquid level. For example, when fluorescence is measured, the intensity of fluorescence F is in proportion to the length of layer L, so that it is in proportion to the quantity of the liquid which is fed into the well, as described in the following expression.F=kl0fecL(k: Proportional Coefficient, I0: Intensity of Excitation Light, f: Quantum Convergence of Fluorescence, e: Molar Absorption Coefficient at Wavelength of Excitation Light, c: Concentration of Fluorescent Material, L: Length of Layer)
Particularly in a typical ELISA based on the measurement of fluorescence, after a target substance is captured by a capturing antibody coated on a wall surface of the well, a detecting antibody bonded to oxygen is fed into the well, and a substrate is finally fed into the well to measure fluorescence due to an enzyme reaction of the substrate. Therefore, the quantity of a fluorescent material produced by an enzyme reaction in a predetermined period of time is determined by the quantity of the captured target substance, so that the concentration of the fluorescent material depends on the quantity of the liquid which is fed into the well. That is, if the quantity of the liquid fed into the well is increased, the concentration of the fluorescent material produced in the predetermined period of time is decreased. Therefore, if the quantity of the liquid fed into the well is increased in order to enhance the sensitivity of measurement, the length of layer L in the above described expression is increased, but the concentration c of the fluorescent material is decreased, so that it is not possible to sufficiently improve the sensitivity of measurement.
Thus, in the conventional method using the microplate, such as ELISA, the antigen-antibody reaction proceeds only on the wall surface of the well coated with the capturing antibody. Therefore, the liquid must be allowed to stand until the reaction occurs after the target substance, antibody and substrate contained in the liquid fed into the well are suspended, circulated and sink to reach the wall surface of the well, so that there is a problem in that the efficiency of reaction is bad. In addition, since the microplate is subdivided into a large number of wells, the quantity of a liquid fed into each of the wells is limited, so that there is a problem in that the sensitivity of measurement is deteriorated. Moreover, in order to increase the height of the liquid, which is filled in each of the wells, from the bottom of the well to the liquid level to prevent the deterioration of the sensitivity of measurement, it is required to increase the quantity of samples and reagents to be used, so that costs are increased.
There is known a method using a porous material as a capturing material as a method for improving the efficiency of reaction and the sensitivity of measurement. However, it is required to provide an external power, such as a pump, in order to control the flowability of the liquid, and it is difficult to continuously control the flowability of the liquid since the porous material is easily clogged up. There is also known a method for fluidizing a liquid by pressurization or suction as a method using a microchip having a fine space to fluidize a liquid in the fine space. However, it is also required to provide an external power and a complicated device in this method. Moreover, there is known a method using a microchip having a fine space to fluidize a liquid in the fine space by a valve structure. However, it is also required to provide power or energy for operating the valve in this method.
In order to improve the sensitivity of measurement and shorten the measuring time in ELISA or the like, there is proposed a microplate capable of increasing the surface area of a reaction surface (capturing surface) to enhance the sensitivity of measurement by forming fine irregularities on the bottom surface of each of wells serving as the reaction surface (see, e.g., Japanese Patent Laid-Open No. 9-159673). There is also proposed a microchip capable of increasing the surface area of a reaction surface to enhance the efficiency of reaction in a fine space by arranging a fine solid particle (bead) as a reaction solid phase in a microchannel of the microchip (see, e.g., Japanese Patent Laid-Open No. 2001-4628). Moreover, there is proposed a microplate capable of increasing the surface area of a reaction surface and saving the quantity of samples by forming a small-diameter recessed portion in the central portion of the bottom of each of wells. (see, e.g., Japanese Patent Laid-Open No. 9-101302).
However, in the microplate proposed in Japanese Patent Laid-Open No. 9-159673, there is a problem in that it is not possible to improve the efficiency of reaction although it is possible to improve the sensitivity of measurement. In addition, the microchip proposed in Japanese Patent Laid-Open No. 2001-4628 is not suitable for the measurement of a large number of specimens although it is possible to improve the efficiency of reaction since it is a microchip having a microchannel structure, not a microplate typically used in ELISA or the like. Moreover, in the microplate proposed in Japanese Patent Laid-Open No. 9-101302, it is not possible to sufficiently improve the efficiency of reaction and the sensitivity of measurement and to save the quantity of samples and reagents to be used, although it is possible to improve the surface area of the reaction surface to some extent.